The following relates generally to memory devices and more specifically to chalcogenide memory device components and chemistry.
Memory devices are widely used to store information in various electronic devices such as computers, wireless communication devices, cameras, digital displays, and the like. Information is stored by programing different states of a memory device. For example, binary devices have two states, often denoted by a logic “1” or a logic “0.” In other systems, more than two states may be stored. To access the stored information, a component of the electronic device may read, or sense, the stored state in the memory device. To store information, a component of the electronic device may write, or program, the state in the memory device.
Multiple types of memory devices exist, including magnetic hard disks, random access memory (RAM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), read only memory (ROM), flash memory, phase change memory (PCM), and others. Memory devices may be volatile or non-volatile. Non-volatile memory, e.g., FeRAM, may maintain their stored logic state for extended periods of time even in the absence of an external power source. Volatile memory devices, e.g., DRAM, may lose their stored state over time unless they are periodically refreshed by an external power source. Improving memory devices may include increasing memory cell density, increasing read/write speeds, increasing reliability, increasing data retention, reducing power consumption, or reducing manufacturing costs, among other metrics.
Chalcogenide material compositions may be used in components or elements of PCM devices. These compositions may have a threshold voltage at which they become conductive (i.e. they switch on to allow current flow). The threshold voltage may change over time, which may be referred to as drift. Compositions that have a higher tendency for voltage drift may limit the usefulness and performance of devices employing those compositions.
Chalcogenide material compositions may also have a memory window that corresponds to a difference in threshold voltage of the chalcogenide material composition when programmed (written) using a voltage having a positive polarity versus when programmed (written) using a voltage having a negative polarity. Compositions that have a smaller memory window may limit the performance of devices employing those compositions.